Use (use-region-p) instead of mark-active
Errors thrown by `error` should not contain "Error:"
Merge pull request #2 from Fuco1/master

Make docstrings comply with emacs standard style
Merge pull request #3 from Fuco1/fix-ov-region

Fix ov region
Merge pull request #4 from Fuco1/fix-error-messages

Fix error messages
Improve ov-read-only
Fix Index links
Add ov-read-only test
Remove redundancy for ov-read-only
Add ov-placeholder
Add contributor
Change ov-keymap macro to ov-keymap function
Change return values to chain operations
Add ov-insert
Fix sticky for ov-insert